Duplexing module for printer

ABSTRACT

A duplexing module that is attachable to a printer that has a simplex media-handling system. The duplexing module is used in conjunction with the simplex system to carry out the print media handling (flipping) that is required for duplex printing. The module includes a single drive roller and an entry guide. The printer feed roller moves the printed media sheet along the entry guide to the drive roller of the duplexing module. The duplexing module includes an exit guide that extends between the drive roller and the feed roller. The print media (having one side printed) moves with the rotated drive roller until it reaches the exit guide. The printed side of the print media is thus directed against the feed roller of the printer so that the opposite side of the media is presented for printing.

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 09/607,679, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/283,107, now U.S. Pat. No. 6,167,231. Both ofthese applications are hereby incorporated by reference.

TECHNICAL FIELD

[0002] This invention relates to methods and apparatus for efficientlymoving print media to enable printing on both sides of the media.Printing on both sides of the media is known as duplex printing.

BACKGROUND OF THE INVENTION

[0003] Duplex printing is a desirable feature in printing systems. Theadvantages of duplex printing include reducing the amount of paperrequired as compared to one-sided (simplex) printing, and generatingprint sets with layouts resembling that of professionally printed books.Conventional duplex printing devices employ complex media handlingmechanisms. Typically, an extra tray is used for temporary storage ofpages having printing on a first side. In an alternative approach, asecond media path is provided to route a first printed page around theexisting paper supply.

[0004] Similarly, duplex copying typically is accomplished by either oneof two methods. In one method, first-side copies are stacked in a duplextray. When a set of first-side copies is complete, the copies are fedout of the duplex tray and returned with an odd number of inversionsalong a duplex path to receive second-side imaging. In an alternativemethod, first-side copies are returned directly to receive second-sideimaging without stacking.

[0005] Conventional duplexing devices tend to have long media paths andmany parts. (Hereafter, the term “paper” and “media” will be usedinterchangeably with the understanding that although paper is a commontype of print media, that term is intended to include any other type ofmedia for receiving printed information thereon.) A substantialchallenge with devices having these complex paper paths is preventingpaper jams and otherwise ensuring that the paper moves smoothly from oneguide or roller to the next.

[0006] Also, as the paper path becomes more convoluted, there is anincreased need for ensuring that the paper does not become skewed as itmoves through the path. Skewing means a slight shifting or rotation ofthe sheet about an axis normal to the surface of the sheet. If a sheetbecomes skewed as it moves between first-side and second-side printing,the second-side printing will not be evenly applied to the sheet.Accordingly, it is important that the paper path associated with aduplexing module be designed to ensure that skew does not occur.Preferably, such a non-skew paper path will be inexpensive to design andmanufacture and require very little maintenance.

[0007] Certain media, such a photographic media, may suffer it isthereafter bent through too small a radius of curvature. For example,such small-radius bending of the sheet may cause the printed sheet tocurl, which is undesirable. Nonetheless, there is oftentimes a need forduplex printing on photographic media. For instance, it may be desirableto print identifying information on the back of a printed, photo qualityimage. It is thus important to minimize the bending of the media (hence,protect against curl) as the photographic media is moved through thepath for such duplex printing.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a duplexing module that isattachable to a printer that has a simplex media-handling system. Theduplexing module is used in conjunction with the simplex system to carryout the print media handling (flipping) that is required for duplexprinting.

[0009] The module of the present invention is intended for use with aprinter that has a feed roller that is rotatable for moving print mediatoward the print source for printing on one side of the media. Therotation of the feed roller is reversible for thereafter moving theprinted media away from the print source and into the adjacent duplexingmodule.

[0010] The duplexing module flips the print media and returns it to thefeed roller with the non-printed side exposed for printing. In thepresent invention, the module includes a drive roller and an entryguide. The entry guide extends between a portion of the drive rollersurface and a location adjacent to the feed roller. When the duplexingmodule is attached to the printer, the printer feed roller is driven tomove the printed media sheet along the entry guide from where the sheetpasses to the drive roller of the duplexing module.

[0011] The duplexing module also includes an exit guide that extendsbetween the drive roller surface and a location adjacent to the feedroller, very near the location where the entry guide joins the feedroller. The print media (having one side printed) moves with the rotateddrive roller until it reaches the exit guide. The printed side of theprint media is directed against the feed roller of the printer so thatthe opposite side of the media is now ready for printing.

[0012] The method and apparatus of the present invention provides a verysimple paper path through the duplexing module. To this end, only asingle drive roller is employed for moving the paper away from and backto the feed roller of the printer. Thus, the manufacturing cost andcomplexity of the module is greatly reduced as compared to morecomplicated mechanisms for advancing the print media through theduplexing module. For example, the use of a single drive rollerminimizes the number of required components (drive shaft, roller “tires”etc.). Also, a single drive roller can be driven by the printer drivemotor using a relatively simple drive connection.

[0013] Moreover, since the media is advanced through the duplexingmodule by a single roller, there is reduced likelihood of paper skewoccurring. The media is substantially wrapped around the drive rollerand rotates with the driver roller through about 270 degrees beforebeing redirected from the drive roller back to the feed roller of thesimplex printing system.

[0014] Another advantage of the use of a single drive roller in theduplexing module (as compared to the use of two or more drive rollers)is that there is reduced likelihood of the paper being stressed as itmoves through the module. Specifically, in a system using two or moredrive rollers the drive speeds of the rollers may not precisely matchbecause of manufacturing tolerances (size of rollers, shafts, gearsetc.). Thus, if the second of a two-roller system is driven slightlyfaster than the first roller, the media will be pulled between the tworollers. The resultant tension in the media produces drag on the systemthat must be overcome with more torque applied to the roller. On theother hand, if the second of a two-roller system is driven slightlyslower than the first roller, the media may become lose or even bunch upbetween the rollers.

[0015] The diameter of the drive roller of the duplexing module isselected to be relatively large. This reduces the radius that the printmedia is wrapped around. The use of a large-diameter roller reduces thetorque that is required to move the media, especially relatively stiffmedia, such as card stock. Reduced torque increases the life of thedrive motor. Thus, the use of a large diameter drive roller expands (fora given applied torque) the range of print media types (stiffness) thatcan be fed through the duplexing module.

[0016] Apparatus and methods for carrying out the invention aredescribed in detail below. Other advantages and features of the presentinvention will become clear upon review of the following portions ofthis specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a block diagram of a duplexing module and print systemaccording to one embodiment of this invention.

[0018]FIG. 2 is a side view diagram of a duplexing module and a simplexmedia handling system according to an embodiment of this invention.

[0019]FIG. 3 is diagram of a transmission and gear linkage forconnecting the simplex media handling system to the duplexing module,thereby to drive the latter.

[0020]FIG. 4 is a simplified diagram primarily illustrating operation ofthe simplex media handing system for printing the first side of a mediasheet.

[0021]FIG. 5 is a diagram illustrating the simplex media handing systemat the completion of first-side printing.

[0022]FIG. 6 is a diagram illustrating transfer of the one-side-printedsheet of media to the drive roller of the duplexing module.

[0023]FIG. 7 is a diagram illustrating the one-side-printed sheet ofprint media being redirected to the feed roller of the simplex mediahandling system in a manner that exposes the non-printed side of themedia for printing thereby to complete the duplex printing operation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Overview

[0024]FIG. 1 illustrates in block diagram a printing system 10 thatincludes a print source 12, a simplex media handling system 14, a drivemotor 16, and a controller 18 with firmware 20. Also included in thesystem 10 is a duplexing module 22. The duplexing module 22 isremovable, allowing the system 10 to be customized for simplex printingand duplex printing.

[0025] Referring to FIG. 2, the print source 12, simplex media handlingsystem 14, and duplexing module 22 are shown for an inkjet printerembodiment. It will be appreciated, however, that the printing systemcan by any of a variety of devices for recording information on one sideof media. The printing system can be, for example, a fax machine orlaser-type printer or copier. Hereafter, however, the preferredembodiment is described in the context of an inkjet printing system.

[0026] The simplex media handling system 14 includes pick roller 59,feed rollers 60, feed idlers 62, a media sensor 72, flag 74, secondaryflag 75, an upper guide 76, and metering rollers 78 with another set ofpinch rollers 80, a pivot mechanism 82 and gear linkage 84. The drivemotor 16 (see FIG. 1) is coupled to the feed rollers 60 and meteringrollers 78 through the gear linkage 84. An opening is included forreceiving the duplexing module 22.

[0027] The duplexing module 22 is removably attached to the simplexmedia handling system 14. The duplexing module includes a sensor 40 thatinterfaces with the controller 18, allowing the controller 18 to detectwhether the duplexing module 22 is attached. An electrical,electro-mechanical, and/or electro-optical connection is included todirect the sensor 40 output to the printer controller 18. The controller18 tests to determine whether the duplexing module 22 is installed.Specifically, if a sensor 40 signal is present, then the module 22 isinstalled (since the sensor is part of the module 22). The controllerfirmware 20 enables both simplex printing and duplex printing operationswhenever the module 22 is attached. If a sensor 40 signal is notpresent, then the controller firmware 20 disables duplex printingoperations and allows only simplex printing operations.

[0028] The printing system 10 receives a media sheet upon which text,graphics or other symbols are to be printed. For example, in this inkjetprinter embodiment the printer receives a print job from a host computer(not shown). The controller 18 controls the printer drive motor 16 andthe print source 12 (such as a conventional inkjet print cartridge) forcoordinating the movement of the media sheet relative to the printsource 12.

[0029] For single-sided (i.e., simplex) printing, the media sheet is fedthrough the simplex media handling system 14 adjacent to the printsource 12 where the text, graphics, or other symbols are recorded on themedia sheet. The sheet is then directed to an output tray 125.

[0030] For duplex printing, the media sheet is fed through the simplexmedia handling system 14 along the same media path used for simplexprinting until the first side of the media sheet is completely printed.The media sheet then is fed back along a portion of that media path intothe duplexing module 22. That module flips the media sheet, and thenreturns the media sheet to the simplex media handling system 14 forsecond-side printing.

[0031] The duplexing module 22 includes the sensor 40, a frame 42, adrive roller 44, a transmission 48, flip guides 64, 66, and pinchrollers 70, 71, 73. The transmission 48 is coupled to the drive motor 16of the printing system, as described more below.

[0032] During duplex printing and after one side of the media sheet hasbeen printed, the sheet is fed into the duplexing module 22. To this endthe simplex media handling system 14 directs the sheet to slide along anentry guide 50 inside the frame 42 toward the drive roller 44. The guide50 terminates at a location adjacent the surface of the drive roller 44so that the media sheet moves into tangential contact with the roller 44to move with the roller, secured thereto by pinch rollers 73.

[0033] The media sheet rotates with the drive roller 44 of the duplexingmodule until the sheet exits the roller 44 onto an exit guide 52 thatdirects the sheet back onto the feed rollers 60 of the simplex mediahandling system 14. Between the time the media sheet leaves and returnsto the feed rollers 60 of the simplex media handling system, therotational direction of the feed rollers 60 is reversed.

[0034] The duplexing module media path is essentially a circular looparound the circumference of the drive roller 44, having an entrylocation 54 in the vicinity of the exit location 56. Both the entrylocation 54 and the exit location 56 are adjacent to a common area ofthe simplex media handling system 14. As the media sheet is directed bythe exit guide 52 into engagement with the feed rollers 60, thenon-printed side of that sheet is exposed to the print source 12 forsecond-side printing and discharge into the output tray 125.

[0035] Referring to FIG. 3, the gear linkage 84 of the simplex mediahandling system 14 is coupled to the transmission 48 of the duplexingmodule. The transmission 48 and gear linkage 84 couple the drive roller44 to the printer drive motor 16. Specifically, when the duplexingmodule 22 is installed, coupling gear 100 is moved (in the directionshown by arrow 26, FIG. 3) into engagement with the gear linkage 84 ofthe simplex media handling system 14 at an interface gear 102. Gearlinkage 84 also includes a drive gear 104, which is coupled to the drivemotor 16 through a linkage included to drive the feed rollers 60 andmetering rollers 78. Thus, it will be appreciated that the drive motorof the printing system is the motive power for the duplexing module.

[0036] The transmission 48 includes a drive gear 86 for engaging theshaft of the drive roller 44. Through a subset of gears 86, 91, 92, 94,95, and 100, the transmission 48 engages the drive roller 44. Asmentioned above, gear 100 serves as a coupling gear that links thetransmission 48 to the gear linkage 84 of the simplex media handlingsystem (e.g., at gear 102). Coupling gear 100 is driven by the printerdrive motor 16 through the gear linkage 84. Transmission gears 91, 92,and 94 are coupled to gear 100, and are mounted to a gear mount 89.

[0037] The rotation of gear 100 (counterclockwise in FIG. 3) causes themount 89 with gears 91, 92 and 94 to rotate about the gear 100 in onedirection 96 (that is, one of two opposing directions 96, 98). Movementof the gears 91, 92, 94 in direction 96 brings gear 92 into engagementwith gear 95, and gear 94 out of engagement with gear 95. Since gear 95is permanently meshed with drive gear 86, this causes drive gear 86 torotate in a counterclockwise direction. In this engagement of gears 92and 95, the transmission 48 is considered to be in first gear.

[0038] The opposite, clockwise rotation of gear 100 (caused by the drivemotor through gear linkage 84) results in movement of the gear mount 89and gears 91, 92, 94 in direction 98, which brings gear 94 intoengagement with gear 95, and gear 92 out of engagement with gear 95,thereby causing drive gear 86 to rotate in the same direction(counterclockwise) as before, even though the coupling gear 100 isrotating in the opposite direction. In this engagement of gears 94 and95, the transmission 48 is considered to be in second gear.

[0039] In first gear, the feed rollers 60 and metering rollers 78 of thesimplex media handling system are rotating in the same(counterclockwise) direction as the drive roller 44 of the duplexingmodule 22. Thus, first gear is employed when the media sheet is to bedirected from the simplex media handling system to the duplexing module.

[0040] In second gear, the feed rollers 60 and metering rollers 78 ofthe simplex media handling system are rotating (clockwise) in theopposite direction as the drive roller 44 of the duplexing module 22.Thus, second gear is employed when the media sheet is to be directedfrom the duplexing module back to the simplex media handling system.

[0041] One preferred embodiment the transmission 48 also includes anoptional clutch 90, which is coupled at one end of the gear mount 89.The other end of the clutch 90 includes a protrusion 99 that moveswithin a cam track (not shown). When the transmission 48 is in neutral,the protrusion 99 sits in a fixed location (e.g., a V-lock groove) ofthe cam track. It takes a change of direction of gear 100 to move theprotrusion out of the V-lock. A gear change (one of gears 92, 94engaging gear 95) may then occur. The clutch 90 moves with gear 94 inthe directions 96, 98. When gear 92 is engaged or gear 94 is engaged,the protrusion 99 does not come to rest in the V-lock. It is when thetransmission 48 is in neutral that the protrusion 99 sits in the V-lock.

[0042] To switch gears from engagement of gear 94 with gear 95 toneutral (the position illustrated in FIG. 3), the drive motor 16 stopsdriving gear 100, then restarts driving gear 100 in the oppositedirection. This moves the gear 94 in direction 96 and brings the clutch90 to rest in neutral (protrusion 99 sits in the V-lock). This isreferred to as a stop and start action. To continue switching gears tobring gear 92 into engagement with gear 95, the direction of gear 100 ischanged again to allow the clutch 90 to come out of neutral, then thedirection is changed one more time to move the gears 92, 94 and clutch90 further along in direction 96. This brings gear 92 into engagementwith gear 95. The actions to switch from neutral to engagement of gear92 (or gear 94) with gear 95 is called a jogging action. Neutral gear isdesirable when, for example, the duplexing module 22 is attached to theprint system 10 but no duplex printing is to occur. Thus the drive motorenergy may be conserved (or used for other purposes) rather than forrotating the duplexing drive roller 44 as would occur if thetransmission were otherwise engaged.

[0043] In a preferred embodiment the feed rollers 60 and meteringrollers 78 are always driven in a common direction during simplex orduplex media handling. That common direction changes during duplexprinting. Irrespective of the position of gears 92, 94, the drive roller44 of the duplexing module rotates in the same direction(counterclockwise in this illustration) even though the feed rollers 60and coupled metering rollers 78 change direction.

[0044] The specific gear linkages for the transmission 48 and linkage 84may vary depending on the specific embodiment. For example the relativepositioning and size of the simplex media handling system 14 andduplexing module 22 may vary, resulting in differing transmission 48 andlinkage 84 embodiments.

Operation

[0045] The media handling operations for simplex and duplex printing aredescribed with reference to FIGS. 4-7. For either simplex or duplexprinting, a media sheet M is lifted into contact with a pick roller 59,which is coaxial with the feed rollers 60. The top sheet M is pickedfrom a stack of media sheets that is held in an input tray 110. Excessmedia sheets are separated from the top sheet by contact with restraintpad system 112 (see FIG. 2).

[0046] The picked media sheet M is fed around feed rollers 60 (FIG. 4).The feed idlers 62 and pinch rollers 70, 71 (FIG. 2) press the mediasheet to the feed rollers 60. The leading edge of the media sheet Mpushes the flip guides 64, 66 out of the media path as the media sheetmoves along the feed rollers 60. Beyond the flip guides 64, 66 the mediasheet moves along a first media path 114. The media path 114 spans apath from pinch rollers 70 to the metering rollers 78 and into a printzone 120 that is adjacent to the print source 12.

[0047] The media sheet is moved between the feed rollers 60 and thepinch rollers 70 under the upper guide 76 and onto the metering rollers78. Pinch rollers 80 press the media sheet to the metering rollers 78.Both the metering rollers 78 and the feed rollers 60 are moving in aforward direction 117 during the first-side printing operation (FIG. 4).

[0048] Eventually, a trailing edge of the media sheet M passes beyondthe feed rollers 60 so that the metering rollers 78 alone move the mediasheet. Beyond the pinch rollers 80, the media sheet is moved along aplatform 118 of the pivot mechanism 82. The print source 12 is locatedadjacent to the platform 118. The media sheet M is fed through the printzone 120, which is between the platform 118 and the print source 12, andinto an output region 122, which in some embodiments includes an outputtray 125.

[0049] For simplex printing, the media sheet is released into the outputregion 122. Thereafter another media sheet may be picked and fed alongthe media path through the print zone for printing. This may be doneimmediately, or after a suitable drying time (depending on the type ofprint source).

[0050] During duplex printing, the trailing edge 124 of the media sheetM (FIG. 5) is not released after the first-side printing. While thepinch roller 80 presses the trailing edge 124 of the media sheet M tothe metering roller 78, the motion of the feed rollers 60 and meteringrollers 78 ceases. A suitable drying time is allowed before the drivemotor 16 reverses the rotational direction of the feed rollers 60 andmetering rollers 78 to a direction 121 (see FIG. 6).

[0051] The sensor 40, which, as explained above, also serves to indicatewhether the duplexing module is installed, may also be (in an embodimentsuch as inkjet printing) a humidity sensor. The sensor 40 detects theambient humidity. Printer controller 18, in response to the detectedhumidity, determines a sufficient drying time before allowing the mediasheet to be moved for second-side printing. In alternative embodiments,separate sensors are used to determine humidity and whether theduplexing module is installed.

[0052] The determination of when to stop the metering rollers 78 withthe media sheet trailing edge 124 grasped is now described withreference to FIGS. 2 and 5. The simplex media handling system 14includes a media sensor 72 and flag 74 (FIG. 2). When the media sheet Mis moved along the first media path 114 from the feed rollers 60 towardthe metering rollers 78, the leading edge of the media sheet trips theflag 74. Once the trailing edge 124 passes beyond the flag, the flag 74returns to its unbiased position. The sensor 72 monitors the media/flagmotion and provides an output signal indicative of when the leading edgeand trailing edge of the media sheet M have passed the flag 74. Theseindications are detected by the controller 18, which then determineswhen the trailing edge 124 of the media sheet M is at the pinch roller80. At such time, the controller 18 has the drive motor 16 discontinuerotation of the feed rollers 60 and metering rollers 78. After aprogrammed pause (e.g., to allow for first-side drying), the controller18 signals to the drive motor 16 to reverse the rotational directions ofthe feed rollers 60 and metering rollers 78 to the reverse direction121.

[0053] Referring to FIG. 6, the metering rollers 78 feed the media sheetM back along the first media path 114 into contact with the feed rollers60. The feed rollers 60 then continue feeding the media sheet away fromthe print source 12. Eventually the media sheet M is out of the grasp ofthe metering rollers 78 and thus moved only by the feed rollers 60 (asdistinguished from both the feed rollers 60 and metering rollers 78).

[0054] The trailing edge 124 of the media sheet M contacts the uppersurface of the entry flip guide 66, which is positioned in its unbiasedposition (FIGS. 2 and 6), thereby to block the media from returning tothe input tray 110 and, instead, redirect the media sheet M over theflip guide 66 and adjacent entry guide 50 so that the media sheet passesinto the entry 54 of the duplexing module 22. The feed rollers 60 thusfeed the media sheet M onto the drive roller 44.

[0055] As the drive motor 16 reverses the directions of feed rollers 60and metering rollers 78 to direction 121 (FIG. 6), the transmission 48moves to second gear (i.e., gear 94 engages gear 95, see FIG. 3). As aresult, when the media sheet is fed from the feed rollers 60 to thedrive roller 44, the drive roller 44 is rotating in a direction 126(counterclockwise in FIG. 6).

[0056] In a preferred embodiment, the duplexing module 22 has a mediapath length from entry location 54 to exit location 56 (FIG. 2) that isat least as long as the maximum rated media sheet length for automaticduplex handling (e.g., 17 inches). The diameter of the drive roller 44is selected to be substantially large (for example, 4 inches or more) sothat the media sheet M is not bent through too small a radius as itmoves through the paper path of the duplexing module. Also, as mentionedabove, the use of a large-diameter drive roller 44 reduces the torquethat is required to move the media sheet, especially relatively stiffmedia, such as card stock. That is, for a given stiffness of media,there is a relatively reduced amount of force required for bending themedia around a relatively increased radius of curvature, thereby tosecure the media to the roller. This reduced force thus reduces thetorque required to rotate the roller and media. Reduced torque increasesthe life (as well as reducing the power requirements) of the drive motor16. Put another way, the use of a large diameter drive roller 44 expands(for a given applied torque) the range of print media types (stiffness)that can be fed through the duplexing module 22.

[0057] Moreover, it will be appreciated that since the media sheet iscarried by a single roller 44 through the duplexing module 22, there isreduced likelihood for skewing of the sheet to occur, as discussedabove. As noted above, the reduction in the number of drive rollers to asingle drive roller 44 in the preferred embodiment of the duplexingmodule 22 reduces the likelihood of the paper being stressed as mightotherwise occur in a system using two or more drive rollers having drivespeeds that are not precisely matched because of manufacturingtolerances (size of rollers, shafts, gears etc.). In short, the paperpath in the duplexing module is essentially a simple, circular oneconforming to about 270 degrees of the periphery of the drive roller 44.

[0058] Prior to the time the media sheet is fed out of the duplexingmodule 22 back onto the feed rollers 60, the feed rollers 60 are drivento change rotational direction from reverse direction 121 back to theforward direction 117. However, owing to the effects of the transmission48 as explained above, the rotational direction of the drive roller 44in the duplexing module remains the same (i.e., direction 126), evenafter the feed rollers 60 go back to the forward rotational direction117.

[0059] The timing for changing directions of the feed rollers 60 back tothe forward direction 117, while the media sheet is in the duplexingmodule 22, is now described. As the media sheet M is fed back along thefirst media path 114 from the metering rollers 78 to the feed rollers 60(FIG. 6), the media sheet trips the secondary flag 75 which trips theflag 74 (see FIG. 2). The flag 74 once tripped, is then released afterthe entire media sheet passes beyond the flags 74, 75. The sensor 72provides to the controller 18 an output signal representing suchtripping indications. The controller knows what direction the drivemotor 16 is rotating the rollers 60, 78, and thus knows that the mediasheet is being fed back for duplex printing.

[0060] Thus, once the media sheet M has passed completely beyond theflag 74, the controller 18 waits a prescribed time (based upon pathlength and feed speed) until the media sheet is off the feed rollers 60and pinch rollers 70 and is moved solely by the rotation of the driveroller 44. In particular, the controller 18 waits until the media sheetis a prescribed distance beyond the feed roller and completely locatedwithin the duplexing module 22. At such time, the controller 18 signalsthe drive motor 16 to change the rotational direction of the feedrollers 60 and metering rollers 78 back to the original forwarddirection 117.

[0061]FIG. 7 shows the media sheet M emerging from the duplexing module22 with the feed rollers 60 of the simplex media handling systemrestarted in the forward direction 117. This stopping and startingaction of the feed rollers 60 (and metering rollers 78) moves the clutch90 (see FIG. 3) causing the second gear 94 to disengage. Specifically,the stopping and starting action puts the transmission 48 into neutral.To shift the transmission 48 out of neutral, and more particularly toengage the first gear 92, rather than the second gear 94, a joggingaction is performed as described above. With the first gear 92 engagedwhile the feed rollers 60 rotate in the forward direction, the driveroller 44 rotates in the desired direction 126 (see FIG. 7).

[0062] With the feed rollers 60 and metering rollers 78 rotating indirection 117 while the drive roller 44 continues to rotate in direction126, the media sheet M is fed out of the duplexing module 22 back ontothe feed rollers 60. As a leading edge of the media sheet exits theduplexing module 22 it moves the flip guide 66 out of its path allowingthe media sheet to be grasped by the feed rollers 60 and pinch rollers70 and moved back onto the first media path 114 (see FIG. 7). The mediasheet M goes over the flip guide 64 and under the flip guide 66. Themedia sheet M is fed along the first media path 114 under the upperguide 76 for leading-edge sensing via sensor 72 and flags 74, 75, andonto the metering rollers 78 and the platform 118, into the print zone120 for second-side printing. The media sheet M is fed through the printzone 120 into the output region 122. The media sheet then is releasedinto the output tray 125.

[0063] Having here described preferred embodiments of the presentinvention, it is anticipated that individuals skilled in the art maymake other modifications thereto within the scope of the invention. Thespirit and scope of the invention is not limited to those embodiments,but extend to the various modifications and equivalents of the inventiondefined in the appended claims.

1. A duplexing module attachable to a printing device that has a feedroller that moves a sheet of print media to and from a print source,comprising: an entry guide located adjacent to the feed roller when theduplexing module is attached to the printing device thereby to receivethe sheet of print media from the feed roller; an exit guide locatedadjacent to the feed roller when the duplexing module is attached to theprinting device to direct the sheet from the duplexing module to thefeed roller; and a drive roller mounted to have surface portionsadjacent to the entry and exit guide members and configured for movingthe sheet from the entry guide to the exit guide.
 2. The module of claim1 further comprising a path along which the sheet moves in the duplexingmodule between the entry and exit guides, the path being substantiallycircular.
 3. The module of claim 2 wherein the drive roller is arrangedso that the sheet moves from the entry guide to the drive roller andfrom the drive roller to the exit guide such that between the entry andexit guides the path of the sheet in the duplexing module substantiallycorresponds to the circumference of the drive roller.
 4. The module ofclaim 3 wherein the path is circular for about 270 degrees.
 5. Themodule of claim 1 wherein the drive roller has a diameter that issubstantially greater than the diameter of the feed roller.
 6. Themodule of claim 1 further comprising gear linkage for connecting areversible drive motor in the printing device to the drive roller of theduplexing module so that the drive motor drives both the feed roller andthe drive roller.
 7. The module of claim 6 including a transmissionconnected between the drive motor and the drive roller for driving thedrive roller in a one direction as the feed roller is driven in eitherof two opposing directions.
 8. A method of making a duplexing module fora printing device that has a feed roller for moving a sheet of printmedia, the method comprising the steps of: providing an entry guidealong which may be slid a sheet of print media away from the feedroller; providing an exit guide along which may be slid a sheet of printmedia toward the feed roller; and mounting a single rotatable duplexingroller so that the entry guide and the exit guide are both substantiallytangent to the periphery of the roller such that a sheet of print mediawill slide from the entry guide, onto the rotating roller and from theroller onto the exit guide.
 9. The method of claim 8 including the stepof arranging the duplexing roller so that the sheet of print media thatis slid onto the roller will be rotated by the roller through about 270degrees.
 10. The method of claim 8 including the step of sizing theduplexing roller to have a radius of about 2 inches.
 11. A method offlipping a sheet of print media to enable printing on both sides of thatsheet, comprising the steps of: directing a sheet of print media from afeed roller to a print source with a first side of the media exposed toreceive printing thereon; moving the sheet from the feed roller onto adrive roller; rotating the drive roller with the sheet thereon;redirecting the sheet from the drive roller back to the feed roller witha second side of the sheet exposed for printing thereon.
 12. The methodof claim 11 including the steps of providing an entry guide between thefeed roller and the drive roller and sliding the sheet along the entryguide from the feed roller to the drive roller.
 13. The method of claim12 including the steps of providing an exit guide between the driveroller and the feed roller and sliding the sheet along the exit guidefrom the drive roller to the feed roller.
 14. The method of claim 11wherein the directing step includes rotating the feed roller in a firstdirection and the redirecting step includes rotating the feed roller ina direction that is opposite the first direction.
 15. The method ofclaim 11 including the step of sizing the drive roller to have adiameter that is greater than the diameter of the feed roller thereby toenable the use of a single drive roller for flipping the sheet.
 16. Themethod of claim 11 wherein the rotating step includes rotating the sheeton the drive roller through about 270 degrees so that upon moving fromthe drive roller the sheet is redirected to a location on the feedroller near a location where the sheet moves from the feed roller duringthe step of moving the sheet from the feed roller onto the drive roller.17. The method of claim 11 wherein the rotating step is carried out witha single drive roller.
 18. The method of claim 14 wherein the driveroller is rotated in only a single direction.
 19. The method of claim 11wherein the rotating step comprises rotating the drive roller in asingle direction irrespective of the rotation direction of the feedroller.